Patients with left ventricular hypertrophy (LVH) have an increased risk of ischemic stroke. Although echocardiography is commonly used for the diagnosis of LVH, there is little information about the potential role of electrocardiography in providing additional prognostic information. The purpose of this study is to determine if electrocardiographically derived criteria for LVH provide additional prognostic value over echocardiography for predicting ischemic stroke in a multiethnic population. A population-based, case-control study was conducted in 177 patients who had had a first ischemic stroke and in 246 control patients matched for age, gender, and race or ethnicity. Left ventricular mass was measured by using 2-dimensional transthoracic echocardiography. Logistic regression analysis was performed to assess the risk of stroke associated with the presence of LVH diagnosed by electrocardiography (defined by 4 established criteria) after adjustment for the presence of other stroke risk factors and for echocardiographically determined LVH. After adjustment for the presence of other established stroke risk factors, ECG-LVH was associated with ischemic stroke, using Sokolow-Lyon (odds ratio [OR] 2.12, 95% CI 1.05-4.30), Cornell voltage (OR 2.06, 95% CI, 1.26-3.35), and Cornell product criteria (OR 2.12, 95% CI, 1.13-3.97). Cornell voltage criterion (men, >2.8 mV; women, >2.0 mV) was associated with ischemic stroke even after adjustment for echocardiographically determined LVH (OR 1.73, 95% CI, 1.04-2.88). The combination of echo-LVH and a positive Cornell voltage criterion was associated with a 3.5-fold increase in stroke risk. Our study indicates that the presence of ECG-LVH is associated with an increased risk of ischemic stroke after adjustment for other stroke risk factors. For Cornell voltage criteria, this relationship persisted even after adjustment for echocardiographic LVH. Electrocardiographic results can provide independent information for left ventricular myocardial changes and should be considered together with echocardiographic results to fully assess the risk of ischemic stroke.